How to remove beading from externally glazed UPVC window?

5 Sep 2012
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United Kingdom
I have a steamed up double glazed unit in an externally beaded UPVC frame. Originally fitted around year 2000 by a local company who are now bust. I expected to remove the internal rubber seal, thus allowing the DGU to be pushed inwards, thus taking the pressure off the external beading, thus allowing external bead removal. However, after a bit of poking around with a small screwdriver, it seems my internal seal isn't rubber, but is perhaps a double sided sticky foam tape? The external seal does seem like it's rubber, but doesn't want to slide out.

How do I proceed - pry off the external beading then cut around the internal tape? Or try harder to remove the external rubber first? And how do I measure the thickness of the existing foam tape?

Thanks in advance :)

Ps this is a different house to a similar question I asked a while ago.
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On an externally beaded system you either have wedge gasket inside which should flick out just like you thought OR you can have the glass bedded on security tape, its only a foam neoprene double sided tape and needs a stanley blade putting through it, this then releases the glass from outside once the beads are removed, the rubber on the bead is highly likely to be part of the bead and does not come away, known as co-extruded bead, co because there are 2 parts, bead and rubber both bonded together during extrusion
Thanks guys, I'll let you know how I get on :)

Edit... any ideas on how to gauge what thickness of security tape I'll need?
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Push a tape measure or steel rule upto the glass inside and measure the thickness like that, or take a close up in focus pic and post here and i'll tell you how thick it is, don't be fooled though, between your thumb and finger it can compress easily, try compressing a full length, its a different story so you have to be within a mm or 2
Hi and thanks for the further reply. Here's a couple of pics with a steel rule held square, tight against the glass. It doesn't seem like the seal 'overhangs' the UPVC frame. It seems to measure 4mm to me but I'd be grateful for any input.
Thanks :)
Window Security Seal 1.jpg
Window Security Seal 2.jpg
To be honest that doesn't look like glazing tape now that I've seen it
Here's a little section I've now prised out. It was fairly easy to slide a small screwdriver between the glass and the trim/seal, but it seemed to be stickier between the trim and the upvc side. It feels more like rubber than a foam type substance, but I'm certain it'll get damaged/stretched if I try to remove it all this way. Any ideas? - your help is much appreciated :)

Window Security Seal 3.jpg
Window Security Seal 4.jpg
It looks like a very fine wedge gasket, can you pull out a corner, need to see if its connected at the corners with the vertical, basically is it 4 pieces of gasket mitred at the corners or is it one long length thats snipped and folded in the corners, if you pull it all out it can be replaced with glazing tape its not a problem
It looks like a very fine wedge gasket, can you pull out a corner, need to see if its connected at the corners with the vertical, basically is it 4 pieces of gasket mitred at the corners or is it one long length thats snipped and folded in the corners, if you pull it all out it can be replaced with glazing tape its not a problem

Thanks for your continued help with this :)

I've dug the seal out a few inches each side of the corner. It's a bit stuck to both the glass and the upvc but I think it's more due to age rather than adhesive (easily unstuck by 'running along' with a blunt stanley blade, ie not actually cutting with the blade). However the actual corner doesn't want to come out without bursting it. What would you do: pull out as much of the seal as possible, or attack the external trim (using the new tool as suggested by Notch7 above)?

I'm hesitant to attack the trim in case it's held under pressure and I break it, since knowing my luck I won't be able to get an exact replacement due to the company going bust (and, for example, replacement cockspur handles aren't available anywhere in the known universe of my type, size and backset).
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Tis a tricky one this without being infront of the window, judging by how much gasket you've already pulled out suggests its not co-extruded with the upvc profile, and because its ext beaded it would point to the rubber being a plain old wedge gasket which pushes the unit out and locks the beads in place, so being a wedge gasket means it should pull out as it was once just pushed in.

Now this is were 30years experience comes in, theres 2 types of external bead, one is a shuffle type security bead, usually used with wedge gasket and 'shuffles' in and out when the gasket inside is fitted, once it shuffles out its locked in, no amount of prying outside will pop the bead out......within reason.

The standard bead doesn't shuffle, it just knocks home with a plastic hammer, this type of bead is generally used with glazing or security tape AND NOT a wedge or co-extruded gasket, main reason is its easy to pop out whether a wedge gasket or any gasket for that matter is used, it is this reason a security tape is used because popping the beads out will still not release the glass, it is effectively glued in until you put a stanley blade through it inside and burglars don't have access to inside at that point yet

So it could be a combination of the wrong gasket and an ordinary standard bead that doesn't shuffle, i would spend a little time with that tool notch linked to( i have about 30 of those) on trying to pop a bead out with the internal rubber in place. If the ext beads are mitred then start in the middle, if scribed its ok to start in the corners
Thanks for all your help mate, I trod carefully and removed the external beading - it came off reasonably easily (the correct tool helped massively tho). The internal rubber seal seems to be formed as one complete shaped rectangle, and is adhered to the internal extrusion (except the bit I cut of course). The external rubber seal is adhered to the beading. There's a short length of approx 6mm thick (please correct me if you think my measuring is wrong) double sided sticky tape mid way along each of the long sides holding the DGU in place.

Window 7.jpg
Window 6.jpg
Window 8.jpg
Ha ha and thats the third type of bead which i was going to mention but thought theres no point as it won't be that type, i haven't seen those in about 20 years easily, think its an old synseal or sheerframe profile and there is a special tool to remove those beads, think from memory it slips down between the outer gasket and glass. It all becomes clear now why the internal gasket isn't acting as a wedge to lock the beads in place because the beads don't shuffle back or forth, the refit the bead first you locate the front lip into the groove and then lower the rear of the bead down, tapping home with a plastic mallet and thats the bead locked in. The double sided tape is security tape and is there as a failsafe in case a burglar got the beads out
I've ordered my replacement and should be fitting it next week or so. What's the technique for fitting the spacers? Obviously I had the frame on a bench, and when sitting the old DGU back in place it stuck to the security tape before I could adjust it centrally to fit the spacers. Is the procedure... to sit the frame upright instead of flat on the bench, put the bottom spacers in place, place the bottom edge of the DGU in place on top of the spacers, adjust it left/right such that I can fit the bottom side spacers, then tilt the DGU backwards into place, fitting the top side spacers as I go, then chap the top ones in at the end?

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